1) Field of the Invention
This invention relates to a printed substrate for mounting a high-power semiconductor chip thereon and also to a driver component making use of the printed substrate.
2) Description of the Related Art
A high-power semiconductor chip for driving a driver component typified by a print head has conventionally been mounted on a chip-on-board printed substrate because of reduce dimension achieved by the use of the printed substrate.
FIG. 2 is a fragmentary cross-sectional view of a chip-on-board, which shows one example of the conventional arrangement. In the chip-on-board, a printed interconnected substrate 20 is constructed of an insulating substrate 21 and a printed interconnected layer 22 provided on a surface of the insulating substrate 21. The printed interconnected substrate 20 is also provided with a heat dissipater 23 disposed on the insulating substrate 21 as a means for permitting the mounting of a high-power semiconductor chip 24. The heat dissipater 23 is made of a metal plate having good thermal conductivity. The semiconductor chip 24 is bonded on the heat dissipater 23 and is connected to the printed interconnected layer 22 via wires 25. The heat dissipater 23, high-power semiconductor chip 24, printed interconnected layer 22 and wires 25, which are all mounted on the printed interconnected substrate 20, are enclosed with a sealing resin 26.
The heat dissipater 23 is provided on the chip-mounting area of the printed interconnected substrate 20, since it is more efficient at dissipating heat, generated in the semiconductor chip 24, not only from the surface of the semiconductor chip 24 but also from the heat spreader 23 having a larger surface area than relying upon the former heat dissipation route alone.
Heat dissipation through a printed interconnected substrate, as described above, is effective for semi-conductor chips of relatively small power consumption, but is insufficient for mounting semiconductor chips of large power consumption exceeding several watts for which the demand has been increasing in recent years. For example, the number of wire dot pins used in a wire dot print head has increased as a result of the recent trend toward higher print quality. This has led to an increase in the electric power (watt) applied to a semiconductor chip for driving the wire dot print head so that the quantity of heat generated in such a semi-conductor chip is ever increasing.